The training from Appleseed and CMP are both good classes for everyone. As to the other classes, $400 a day is pretty pricey – that’s what I charge for a 3 day class. Some guys with the big reputations get that much, but most aren’t worth it. $250-$300 for a 16-20 hour class is reasonable for a class that covers anything more than the basics. I charge more because I do a 30 hour class in 3 days and do several low light drills at night and force on force training.
For those outside of the US, get a better quality airsoft (try to get a copy of a gun that would be reasonable for you to ‘find’ in an emergency) and practice. Start very close range – feet not yards/meters. Start slow and learn trigger control and sight picture. Then learn to point and fire – for reactionary situations. Then start moving and firing. Learn how to clear corners and shot from any position imaginable. Then you go back to the basics and repeat the whole process.